The distribution of fractured cracks is an important measurement of a physical quantity in a hydraulic fracturing test of rocks. Presently, observing cracks in a hydraulic fracturing test of rocks mainly depends on the technology of acoustic emission monitoring and CT imaging with x-rays. The technology of acoustic emission monitoring is extremely useful in acoustic signal acquisition during the fracturing of rocks. However, it has poor precision in retrieving locations of acoustic signals, especially for examining small dimension samples in a laboratory setting, and it is unable to obtain a relatively precise distribution of fractured cracks. In contrast, CT imaging has higher precision in locating fractured cracks, but a low resolution for cracks with average widths, losing information of the distribution of a number of significant cracks.
Therefore, current methods for observing cracks during a hydraulic fracturing test of rocks fail to satisfy the needs of accurately observing the distribution of cracks in said hydraulic fracturing test of rocks.